Radio communication systems have limitations with respect to the number of users which can be active in a given geographic area. The limitations depend on the size of the geographic area, the propagation losses in the area, the statistics for usage-period duration and interval, any system-idle background usage, and the radio communication system physical parameters.
How particular types of radio systems handle too many users varies. In one prior art digital enhanced cordless telecommunications (DECT) system, in cases where usage is carrier-to-interferer limited, the system may offer reduced range for acceptable audio quality. Alternatively, the system may refuse to allow new links to be established in cases where usage for a particular channel and timeslot combination is allowed only if interference in that combination is lower than a threshold, and that threshold is exceeded by the propagating interfering signal from a not-so-distant user in another communications link.
The density of users the system can handle trades off with range due to other-user interference imposing a noise floor for the radio signal's SNR. In the prior art, a variety of attempts to address the range vs. density problem have been tried. In one prior art attempt, the transmit power of the unit is adjusted in response to the received signal level. For this approach, at strong received signal levels the transmit signal is reduced. The success of this approach is limited by the fact that if the individual units are interference-limited in range even at low power, and for a system where all units are at the same power level, it does not matter what the actual power level is, as the receiver's signal-to-interference level is the same. Units which are at a range where they are no longer at low power are a degradation to the all-units-at-the-same-power case. Adjusting transmit power in response to received signal level works to improve density only if most units adjust their transmit power downwards far enough that range is limited by signal-to-thermal-noise rather than signal-to-interference. This is commonly not the case for a non-line-of-sight environment such as a head-worn product where the user can shadow the antenna path between the base and headset even at close range.
As a result, improved methods and apparatuses for improved range and density are needed.